The use of compressed gas frequently requires a regulator connected between the gas cylinder and the point of end use of the gas. For example in oxyacetylene welding, a regulator is used between each gas cylinder and the welding torch. The regulators can be adjusted to control the pressure and the rate of flow of gas to the torch. Connection of a regulator to a gas cylinder is usually accomplished through an inlet conduit that extends from the regulator housing and that has an internally threaded nut journaled on its end. The regulator inlet conduit is shaped to mate with an externally threaded conduit extending from the valve housing on top of the gas cylinder. Threaded engagement between the internally threaded nut and the valve housing conduit secures the connection and makes it air tight.
Regulators are comparatively small and expensive, and are therefore subject to theft. Removal of a regulator from a gas cylinder simply involves unscrewing a single nut. There is therefore a need for an effective device for locking or otherwise securing regulators to cylinders. Prior security devices, however, are in varying degrees unsuitable for this purpose.
One class of prior security devices, adapted primarily for securing the union between two gas lines, comprises a pair of casing sections that can be joined together around the union and locked to one another. One limitation of such devices is that they are secured against axial movement only by interference between the closed casing sections and the union nut, and different security devices must therefore be used for different sizes of gas line. A further limitation of such devices is that someone attempting unauthorized disconnection can often crimp the device such that the casing simply becomes an extension of the nut, permitting rotation of the nut through the casing and disconnection of the pipes.